CN104154869B - White light interference lens center thickness measuring system and method - Google Patents

Abstract

The invention discloses a system and method for measuring the central thickness of a white light interference lens, belonging to the technical field of optical precision measurement. The technical problems of low measuring precision and small measuring dynamic range of the existing lens center thickness measuring device are solved. The white light interference lens central thickness measuring system of the present invention comprises a supercontinuum light source, a photodetector, a 1:1 fiber coupler, a measuring arm, a reference arm, a first optical fiber, a second optical fiber, and a data processing unit; wherein, the measuring arm It includes a third optical fiber and a focusing mirror, and the reference arm includes a fourth optical fiber, a self-focusing lens, a scanning angle mirror, a plane mirror, a displacement mechanism and a length measuring interferometer system. The accuracy of the system can reach 0.2μm (3σ), and the dynamic range can reach 1.5m.

Description

System and method for measuring center thickness of white light interference lens

technical field

The invention relates to a system and method for measuring the central thickness of a white light interference lens, belonging to the technical field of optical precision measurement.

Background technique

In the field of optics, the three basic parameters of a lens are central thickness, refractive index and radius of curvature. The processing accuracy of the central thickness of the lens will directly affect the overall performance of the lens such as focal length and aberration, and then affect the performance of the entire optical system. In the installation and adjustment of the optical system, the optical axis deflection angle, radial offset and axial clearance of the lens need to be precisely adjusted according to the center thickness of the lens. Therefore, the higher the measurement accuracy of the lens center thickness, the more difficult and expensive the installation and adjustment lower. With the emergence of ultra-precision engineering such as lithography objective lens and nuclear fusion optical system, more stringent requirements are put forward for all optical parameters including lens center thickness. Whether it is to ensure that the optical lens processing meets the design tolerance requirements, or to reduce the difficulty and cost of assembly and adjustment, it is necessary to have high-precision optical testing instruments to detect its parameters item by item, thereby eliminating its processing deviation.

At present, the technology of measuring lens thickness can be divided into contact type and non-contact type.

Contact measurement, usually with a hand-held dial gauge or micrometer. During measurement, the accuracy of the center point of the lens will directly affect the measurement accuracy, so the inspector needs to move the measured lens back and forth during measurement to find the highest point (convex lens) or the lowest point (concave lens), so the measurement speed is slow and the error is large. And the frequent movement of the measuring head is easy to scratch the surface of the lens.

Non-contact measurement methods include image method, co-planar method, white light confocal method and interferometry. The lens center thickness measurement by image method is affected by the camera imaging system, CCD resolution, image clarity and calibration coefficient accuracy, and the measurement error is within 15 μm. The coplanar capacitance method is a relative measurement. In order to obtain reliable data as the basis for detection, a coplanar capacitance probe is required to accurately test the material of the tested lens. The measurement process is complicated, which is not conducive to the measurement of the thickness of the lens center, and the measurement error about 5 μm. The white light confocal method uses the probe formed by the axial chromatic aberration after the white light passes through the lens to locate the apex of the surface of the tested lens, and then calculates the thickness of the lens through the spectral information reflected by the apex of the upper and lower surfaces of the tested lens. However, this method has low focus sensitivity and resolution, and the working distance is limited (30μm-25mm).

There are two main types of interferometric lens center thickness measuring devices: the first is an optical measuring instrument for the thickness of an optical element (CN87200715), which includes two Michelson interferometric systems. The surface is positioned, and then the lens under test is compared with the standard block to obtain the center thickness of the lens under test. However, the structure of the measuring device is complex, and components need to be replaced during the measurement process. The measurement accuracy not only depends on the positioning accuracy of multiple surfaces, but also depends on the accuracy of the known thickness of the standard block. The second is the LenScan series products launched by Fogale Nanotech in France, which use a short coherent light source to build a Michelson interferometer, and use the precise movement of the scanning reference mirror to find different white light interference fringes and achieve precise positioning of different mirror positions. The maximum measurement dynamic range of the LenScan series products is 600mm (optical thickness), the central wavelength of the broadband light source is about 1310nm, the bandwidth is 30nm, the coherence length is 25μm, and the air gap measurement accuracy reaches 0.3μm (3σ), and in the actual measurement, Affected by the measurement environment, the stability of the scanning mirror, and the jitter of the light intensity, the measurement accuracy of the lens center thickness is about 2 μm (3σ).

In the optical recalculation and system adjustment of the objective lens system of the lithography machine, the accuracy of the lens center thickness and spacing measurement is required to reach 0.5μm (3σ), and the measurement dynamic range is expected to be above 1.0m. The lens center thickness measuring device in the prior art cannot meet this requirement.

Contents of the invention

The object of the present invention is to provide a white light interference lens center thickness measurement system and method to solve the technical problems of low measurement accuracy and small measurement dynamic range of the existing lens center thickness measurement device.

The technical solution adopted by the present invention to solve the problems of the technologies described above is as follows:

White light interference lens center thickness measurement system, including supercontinuum light source, photodetector, 1:1 fiber coupler, measuring arm, reference arm, first optical fiber, second optical fiber and data processing unit;

The measuring arm includes a third optical fiber and a focusing mirror;

The reference arm includes a fourth optical fiber, a self-focusing lens, a scanning angle mirror, a plane mirror, a displacement mechanism and a length measuring interferometer system;

The focusing mirror and the measured lens are on the same optical axis;

The displacement mechanism includes a displacement guide rail and a mobile bracket that can perform scanning motion on the displacement guide rail. The scanning angle mirror is fixed on one side of the mobile bracket, and the measurement angle mirror of the length measuring interferometer system is fixed on the side of the mobile bracket. On the other side, the optical axis of the scanning corner reflector is parallel to the optical axis of the length-measuring interferometer system, the moving bracket moves along the optical axis direction of the scanning corner reflecting mirror, the length-measuring interferometer system measures the displacement of the moving bracket, and the displacement The data is transmitted to the data processing unit;

The white light emitted by the supercontinuum light source is transmitted to the 1:1 fiber coupler through the first optical fiber, and is divided into two beams. One beam enters the focusing mirror through the third optical fiber, and then enters the lens under test through the focusing mirror, and then passes through the After being reflected by the front and rear surfaces of the measurement lens in turn, it returns to the 1:1 fiber coupler along the original path; the other beam enters the self-focusing lens through the fourth optical fiber, and then enters the scanning angle mirror through the self-focusing lens, and then reflects through the scanning angle mirror to the plane reflector, and then return to the 1:1 fiber coupler along the original path after being reflected by the plane reflector, the outgoing light of the measurement arm and the reference arm are coupled into the second optical fiber through the 1:1 fiber coupler and generate interference light signal, the photodetector receives the interference light signal from the second optical fiber, converts the interference light signal into an electrical signal, and transmits it to the data processing unit. The data processing unit processes the interference light signal, and combines the movement measured by the length measuring interferometer The displacement of the bracket, the displacement of the mobile bracket corresponding to the center position of the maximum interference light signal is obtained, and the center thickness of the measured lens is calculated according to the displacement;

The light path of the self-focusing lens incident on the scanning corner reflector is parallel to the light path of the incident plane reflector of the scanning corner reflector.

Further, the wavelength range of the supercontinuum light source is 470-1700nm.

Further, the length of the third optical fiber is equal to the length of the fourth optical fiber.

Further, the focusing mirror is a continuous focusing system.

Further, the measurement system further includes a main control computer running a data processing unit, and the main control computer is respectively connected with the photodetector and the length measuring interferometer system.

Further, the measurement system also includes an electromechanical control system for controlling the movement of the mobile support.

Further, the measurement system further includes an adjustment mount for fixing the measured lens and adjusting the optical axis of the measured lens.

Further, the measurement system also includes an environment control system for controlling the temperature, humidity and air pressure of the measurement environment.

Further, the center position of the maximum white light interference signal is judged by a center of gravity algorithm.

The method for detecting the center thickness of the lens by the white light interference lens center thickness measuring system includes the following steps:

Step 1. The data processing unit calculates the air refractive index n ₁ at the temperature T _{1 , the pressure P 1 and the wavelength λ 1 of the laser head of the length measuring interference system according to the input related parameters, and at the temperature T 1 , pressure P 1} and super The air group refractive index n ₂ at the wavelength λ ₂ of the continuum light source, and the group refractive index n ₃ of the measured lens at the temperature T ₂ , the pressure P ₂ and the wavelength λ ₂ of the supercontinuum light source;

Step 2. Adjust the optical axis of the tested lens and the focusing mirror so that the reflected light from the front and rear surfaces of the tested lens can return to the 1:1 fiber coupler through the focusing mirror;

Step 3: Control the mobile support to perform scanning motion along the optical axis of the scanning angle mirror, and the data processing unit processes the interference light signal obtained by the photodetector to obtain the displacement Z _of the mobile support corresponding to the center position of the maximum interference light signal and Z2 _;

Step 4, the data processing unit according to the following formula:

Calculate the central thickness D of the tested lens.

Further, the data processing unit uses dispersion formula and Edlén formula to calculate n ₁ , n ₂ and n ₃ .

Compared with prior art, the beneficial effect of the present invention:

(1) The light source in the white light interference lens center thickness measurement system of the present invention is a supercontinuum light source, the wavelength range is 470-1700nm, and the bandwidth is 1230nm, so that the coherence length of the light source is shorter, and it is more sensitive to zero optical path difference. Interpretation of the central position of the fringes is more accurate, so that the theoretical accuracy of lens center thickness measurement can reach 0.2μm (3σ);

(2) The white light interference lens central thickness measuring system of the present invention has increased focusing lens in measuring arm, by focusing, the intensity of the return light of the measured lens at different positions is adjusted, improved signal-to-noise ratio, can simultaneously Precise positioning and measurement of multiple lenses;

(3) The white light interference lens central thickness measurement system of the present invention introduces a scanning angle reflector in the reference arm to form a folded optical path, which not only makes the dynamic range of measurement reach 1.5m, but also does not change the incident angle during the movement of the scanning angle reflector. The direction of light and reflected light improves the vibration resistance of the system.

Description of drawings

Fig. 1 is a schematic structural view of a white light interference lens central thickness measurement system of the present invention;

Fig. 2 is the spectrogram of supercontinuum light source of the present invention;

In the figure, 1. Supercontinuum light source, 2. Photodetector, 3. 1:1 fiber coupler, 4. Measuring arm, 5. Reference arm, 6. First optical fiber, 7. Second optical fiber, 8. The first Three optical fibers, 9, fourth optical fiber, 10, focusing mirror, 11, measured lens, 12, self-focusing lens, 13, scanning angle reflector, 14, plane reflector, 15, displacement mechanism, 151, mobile bracket, 152. Displacement guide rail, 16. Length measuring interferometer system, 161. Measuring angle reflector, 162. Laser head, 17. Main control computer, 18. Electromechanical control system, 19. Adjusting frame.

detailed description

Further illustrate the present invention below in conjunction with accompanying drawing.

As shown in Figure 1, the white light interference lens center thickness measuring system of the present invention comprises: a supercontinuum light source 1, a photodetector 2, a 1:1 fiber coupler 3, a measuring arm 4, a reference arm 5, a first optical fiber 6, Second optical fiber 7 and data processing unit, wherein, measuring arm 4 comprises the 3rd optical fiber 8 and focusing mirror 10, and reference arm 5 comprises the 4th optical fiber 9, self-focusing lens 12, scanning angle reflector 13, plane reflector 14, Displacement mechanism 15 and length measuring interferometer system 16.

The supercontinuum light source 1 is connected with the 1:1 fiber coupler 3 through the first optical fiber 6; the photodetector 2 is connected with the 1:1 fiber coupler 3 through the second optical fiber 7; one end of the third optical fiber 8 is connected with the 1:1 optical fiber The coupler 3 is connected, and the other end is aimed at the focusing lens 10 and is coaxial with the focusing lens 10; one end of the fourth optical fiber 9 is connected with the 1:1 fiber coupler 3, and the other end is aimed at the self-focusing lens 12 and is connected with the self-focusing lens 12. The focusing lens 12 is on the same optical axis; the third optical fiber 8 and the fourth optical fiber 9 are equal in length within the error tolerance range, which can avoid the optical path error caused by thermal expansion difference and improve the detection accuracy; the displacement mechanism 15 includes a mobile bracket 151 and a displacement Guide rail 152, the bottom end of movable support 151 is arranged on displacement guide rail 152, and movable support 151 can do scanning motion on displacement guide rail 152 along the optical axis direction of scanning angle reflector 13; One side; length measuring interferometer system 16 is prior art, mainly comprises measuring angle reflector 161 and laser head 162 that are arranged along the same optical axis, and measuring angle reflector 161 is fixed on the other side of movable bracket 151, and length measuring The optical axis of the interferometer system 16 is parallel to the optical axis of the scanning angle reflector 13, and the length-measuring interferometer system 16 measures the displacement of the movable support 151, and transmits the displacement to the data processing unit in real time, because the scanning angle reflector 13 is also Fixed on the movable support 151, and the scanning angle reflector 13 is parallel to the optical axis of the length measuring interferometer system 16, the movable support 151 moves along the optical axis direction of the scanning angle reflector 13, so the displacement is also the scanning angle reflector 13 displacements;

The light emitted by the supercontinuum light source 1 is transmitted to the 1:1 fiber coupler 3 through the first optical fiber 6, and the 1:1 fiber coupler 3 divides the light into two beams, one beam enters the measurement arm 4, and the other beam enters the reference arm 5 Middle; the light beam entering the measuring arm first enters the focusing mirror 10 through the third optical fiber 8, then after being focused by the focusing mirror 10, it converges on the measured lens 11 on the same optical axis as the focusing mirror 10, and then passes through the After the front and rear surfaces of the measurement lens 11 reflect sequentially, they return to the 1:1 fiber coupler along the original path; the light beam entering the reference arm 5 first enters the self-focusing lens 12 through the fourth optical fiber 9, and then the incident scanning angle reflection through the self-focusing lens 12 Mirror 13 is reflected to plane reflector 14 through scanning angle reflector 13 again, and after plane reflector 14 is reflected, returns 1:1 optical fiber coupler 3 along the original path, wherein from self-focusing lens 12 incident scanning angle reflector 13 The light is parallel to the light reflected by the scanning corner reflector 13 to the plane reflector 14; then the outgoing light of the reference arm 5 and the outgoing light of the measuring arm 4 enter the second optical fiber 7 through the 1:1 fiber coupler 3 and interfere with each other. Interfering optical signals are generated, and the interfering optical signals are transmitted to the photodetector 2 through the second optical fiber 7. After the photoelectric detectors 2 convert the interfering optical signals into electrical signals, they are transmitted to the data processing unit. The data processing unit uses the center of gravity algorithm to analyze the interfering optical signals Processing, combined with the displacement of the moving bracket 151 measured by the length measuring interferometer system 16, the displacement of the moving bracket 151 corresponding to the center position of the maximum value of the white light interference signal (ie: the displacement of the scanning angle mirror 13) Z1 and Z2, and then calculate the central thickness of the measured lens 11 according to the displacement amount and the relationship between the refractive index.

The principle of the present invention is: the scanning angle reflector 13 is driven by the movable bracket 151 to scan, and when the scanning angle reflector 13 moves to a certain position, the optical path difference between the measuring arm optical path and the reference arm optical path is zero, When the first maximum white light interference signal appears, it is received by the photodetector 2 and displayed on the display screen. Using the center of gravity algorithm and the displacement recorded by the length measuring interferometer system 16, the center position corresponding to the first maximum white light interference signal is obtained. The displacement Z ₁ of the scanning angle reflector 13; continue to move the scanning angle reflector 13 until the second maximum white light interference signal appears, and use the same method to obtain the scanning angle corresponding to the center position of the second maximum white light interference signal The displacement of mirror 13 is Z ₂ .

In this embodiment, the data processing unit can also calculate the air refractive index n ₁ at temperature T ₁ , pressure P ₁ and laser head wavelength λ ₁ , and at temperature T ₁ , pressure P ₁ and supercontinuum light source wavelength λ The air group refractive index n ₂ at ₂ , the group refractive index n ₃ of the measured lens 11 under the temperature T ₂ , pressure P ₂ and supercontinuum light source wavelength λ ₂ , the formula for calculating the central thickness can be:

In this embodiment, the measurement system may further include a main control computer capable of running a data processing unit, and the main control computer is connected to the photodetector 2 and the length measuring interferometer system 16 respectively.

In this embodiment, the measurement system may also include an electromechanical control system 18 connected to the displacement mechanism 15 and controlling the moving bracket 151 to perform scanning motion. The electromechanical control system 18 may be connected to the main control computer 17 and controlled by the main control computer 17.

In this embodiment, the measurement system may also include an adjustment mount 19 that fixes the measured lens 11 and adjusts the optical axis of the measured lens 11. The measured lens 11 is clamped by the adjustment mount 19. By adjusting the inclination and translation of the adjustment mount 19, the The lens under test 11 has the same optical axis as the focusing mirror 10, which reduces the measurement error caused by the offset of the optical axis.

In this embodiment, the measurement system may also include an environment control system, which is placed in the measurement environment where the white light interference lens center thickness measurement system is located, and precisely controls the temperature, humidity and air pressure of the measurement environment.

In this embodiment, the supercontinuum light source 1 is an existing technology, including a pump laser, a focusing lens, a photonic crystal fiber, a fiber connector and a polarization-maintaining fiber. The light emitted by the laser is converged to the end face of one side of the photonic crystal fiber through the focusing lens. The cut of the end face is required to be smooth and perpendicular to the optical axis. After the light enters the photonic crystal fiber, due to the high nonlinearity of the photonic crystal fiber, supercontinuum white light is generated. The other end of the photonic crystal fiber is connected to the polarization-maintaining fiber through a fiber connector to output supercontinuum white light. In this embodiment, the central wavelength of the pump laser is 1060 nm, the photonic crystal fiber is about 20.0 m long, the core diameter is 5.0 μm, the air hole diameter is 2.2 μm, the hole spacing is 3.4 μm, and the cladding diameter is 125.0 μm. Figure 2 is the spectrum diagram of the supercontinuum light source 1. It can be seen from the figure that the white light spectrum generated by the photonic crystal fiber is very wide, the bandwidth δλ is 1230nm, and the central wavelength λc is about 1085nm. The coherence calculated by formula (2) The length Δl is 0.42 μm;

As shown in Figure 2, the white light spectrum generated by the photonic crystal fiber is affected by the injection light of the pump laser except around 1060nm. requirements. The supercontinuum light source 1 shortens the coherence length of the light source, is more sensitive to zero optical path difference, and interprets the position of the center of gravity of the interference fringes more accurately, so that the theoretical accuracy of the center thickness measurement of the tested lens 11 can reach 0.2 μm (3σ).

In this embodiment, the vertical distance from the self-focusing lens 12 to the scanning corner mirror 13 can reach up to 0.75m, and the vertical distance from the plane mirror 14 to the scanning corner mirror 13 can reach up to 0.75m. The mirror 13 forms a folded optical path, so that the dynamic range of the measurement reaches 1.50m, and the movement of the scanning corner mirror 13 does not change the propagation direction of the reference light, which enhances the anti-vibration capability.

In this embodiment, the focusing mirror 10 is preferably a continuous focusing system, and the focusing range of the focusing mirror 10 is 5m-15m, which can converge the light emitted by the third optical fiber 8 to different positions of the tested lens 11, and the The intensity of the light reflected by the measuring lens 11 is modulated, the signal-to-noise ratio is improved, and multiple lenses are precisely positioned and measured at the same time.

The white light interference center thickness measurement system of the present invention detects the lens center thickness method, comprising the following steps:

Step 1, start the data processing unit, input relevant parameters, relevant parameters include: the temperature T ₁ of the optical path of the reference arm and the pressure P ₁ of the optical path of the reference arm; the temperature T ₂ of the optical path of the measuring arm and the pressure P ₂ of the optical path of the measuring arm; the laser head The wavelength λ ₁ of 162; the wavelength λ ₂ of the supercontinuum light source 1; the refractive index of the measured lens 11 at a fixed wavelength (commercially purchased or molded lenses will give a certain refractive index at a certain wavelength) and dispersion coefficient;

Using the dispersion formula:

and Edlén's formula:

In the formula (3)-(5), n _g represents the group refractive index; n represents the real-time refractive index of air; Indicates the dispersion coefficient, and the dispersion coefficient will change different values according to the temperature and pressure; λ is the wavelength in vacuum, the unit is μm, n _s is the refractive index of air in the standard state, t, p are the temperature and pressure of the measurement environment, and the corresponding units are °C, torr;

Calculate the air refractive index n ₁ at temperature T ₁ , pressure P ₁ and laser head 162 wavelength λ ₁ (substitute λ ₁ into (4) formula to get n _s first, then substitute n _s into (5) formula to get n ₁ ), the air group refractive index n ₂ at temperature T ₁ , pressure P ₁ and supercontinuum light source 1 wavelength λ ₂ (substituting the calculated n ₁ into (3) formula, in (3) formula at this time wavelength λ is λ ₂ , and n ₂ is obtained), and the group refractive index n ₃ of the measured lens 11 at temperature T ₂ , pressure P ₂ and supercontinuum light source 1 wavelength λ ₂ (the measured lens 11 is measured at a certain wavelength The refractive index of (3) is substituted into (3) formula, and wavelength λ is λ ₂ in (3) formula at this moment, calculate and obtain n ₃ ), above-mentioned calculation process is prior art;

Generally, the main control computer 17 is used to run the data processing unit;

Step 2, adjust the optical axis of the measured lens 11 and the focusing mirror 10, so that the reflected light on the front and rear surfaces of the measured lens 11 can return to the 1:1 fiber coupler 3 through the focusing mirror 10;

Generally, the lens under test 11 is clamped by the adjustment frame 19. By adjusting the tilt and translation of the adjustment frame 19, the lens under test 11 and the focusing mirror 10 have the same optical axis, reducing the measurement error caused by the offset of the optical axis;

Step 3, control the mobile bracket 151 to perform scanning motion along the direction of the optical axis of the scanning corner mirror 13 (the moving bracket 151 moves to drive the scanning corner mirror 13 and the measuring corner mirror 161 to move), and the data processing unit utilizes the center of gravity algorithm to analyze the interference light signal Processing, combined with the displacement measured by the length-measuring interferometer system 16, the displacements Z1 and Z2 of the mobile support 151 (scanning angle mirror 13) corresponding to the center position of the maximum interference optical signal are obtained (the data processing unit utilizes the received pole The large interference light signal determines that the optical path difference between the optical path of the reference arm and the optical path of the measuring arm returned by the front and rear surfaces of the measured lens 11 is zero), then according to the formula:

Calculate the value of the center thickness D of the measured lens 11;

Generally, the mobile bracket 151 is driven and controlled by the electromechanical control system 18 , and the electromechanical control system 18 can be controlled by the main control computer 17 and connected with the displacement mechanism 15 .

Apparently, the descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those of ordinary skill in the technical field, without departing from the principle of the present invention, some improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention .

Claims (10)

1. white light interference lens center thickness measuring system, it is characterised in that including super continuum source (1), photodetector (2)、1:1 fiber coupler (3), measuring arm (4), reference arm (5), the first optical fiber (6), the second optical fiber (7) and data processing list Member；

The measuring arm (4) includes the 3rd optical fiber (8) and focusing lens (10)；

The reference arm (5) includes the 4th optical fiber (9), GRIN Lens (12), scanning corner reflector (13), plane mirror (14), displacement mechanism (15) and length-measuring interferometer system (16)；

The focusing lens (10) and measured lens (11) same to optical axis；

Institute's displacement mechanism (15) includes displacement guide rail (152) and can make the movement of scanning motion on displacement guide rail (152) Support (151), the scanning corner reflector (13) is fixed on the side of mobile support (151), the length-measuring interferometer system (16) scanning corner reflector (161) is fixed on the opposite side of mobile support (151), the optical axis of scanning corner reflector (13) and survey The optical axis of long interferometer system (16) is parallel, optical axis direction motion of the mobile support (151) along scanning corner reflector (13), surveys length The displacement of the mobile support (151) of interferometer system (16) measurement, and displacement is transmitted to data processing unit；

The light of super continuum source (1) transmitting is transmitted to 1 through the first optical fiber (6):1 fiber coupler (3), is divided into two beams, It is a branch of through the incident focusing lens (10) of the 3rd optical fiber (8), then through the incident measured lens (11) of focusing lens (10), then through measured lens (11) after front and rear surfaces reflect successively, along backtracking 1:1 fiber coupler (3), another beam is incident certainly through the 4th optical fiber (9) Condenser lens (12), then through GRIN Lens (12) incident scan angle speculum (13), then scanned corner reflector (13) is anti- Plane mirror (14) is incident upon, and along backtracking 1 after plane mirror (14) reflection:1 fiber coupler (3), measuring arm (4) emergent light and the emergent light of reference arm (5) is through 1:1 fiber coupler (3) is coupled into the second optical fiber (7) and produces interference Optical signal, photodetector (2) receives the interference light signal from the second optical fiber (7), and interference light signal is converted into telecommunications Transmitted after number to data processing unit, data processing unit is handled interference light signal, with reference to the length-measuring interferometer of reception The displacement of the mobile support (151) of system (16) measurement, obtains the corresponding mobile support in very big interference light signal center (151) displacement, and according to the center thickness of the displacement calculation measured lens (11)；

The light path and scanning corner reflector (13) plane of incidence of GRIN Lens (12) the incident scan angle speculum (13) are anti- The light path for penetrating mirror (14) is parallel；

The white light interference lens center thickness measuring system detects lens center thickness method, comprises the following steps：

Step 1: data processing unit is calculated in temperature T according to the relevant parameter of input₁, pressure P₁With length-measuring interferometer system (16) laser head (162) wavelength X₁Under air refraction n₁, in temperature T₁, pressure P₁With super continuum source (1) wavelength X₂ Under air group index n₂, and in temperature T₂, pressure P₂With super continuum source wavelength X₂Group's refraction of lower measured lens (11) Rate n₃；

Step 2: regulation measured lens (11) and focusing lens (10) same to optical axis, makes the reflected light of measured lens (11) front and rear surfaces 1 can be returned to by focusing lens (10):1 fiber coupler (3)；

Step 3: the mobile support (151) of control does scanning motion, data processing unit along scanning corner reflector (13) optical axis direction The interference light signal that photodetector (2) is obtained is handled, the corresponding movement in very big interference light signal center is obtained The displacement Z of support (151)₁And Z₂；

Step 4: data processing unit is according to below equation：

<mrow> <mi>D</mi> <mo>=</mo> <mfrac> <mrow> <msub> <mi>n</mi> <mn>2</mn> </msub> <mo>&amp;CenterDot;</mo> <mn>2</mn> <mrow> <mo>(</mo> <msub> <mi>Z</mi> <mn>2</mn> </msub> <mo>-</mo> <msub> <mi>Z</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>n</mi> <mn>1</mn> </msub> <mo>&amp;CenterDot;</mo> <msub> <mi>n</mi> <mn>3</mn> </msub> </mrow> </mfrac> </mrow>

Calculating obtains the center thickness D of measured lens (11).

2. white light interference lens center thickness measuring system according to claim 1, it is characterised in that the super continuous spectrums The wave-length coverage of light source (1) is 470-1700nm.

3. white light interference lens center thickness measuring system according to claim 1, it is characterised in that the 3rd optical fiber (6) and the 4th optical fiber (7) equal length.

4. white light interference lens center thickness measuring system according to claim 1, it is characterised in that the focusing lens (10) it is continuous focusing system.

5. white light interference lens center thickness measuring system according to claim 1, it is characterised in that also including operation number According to the main control computer (17) of processing unit, the main control computer (17) respectively with photodetector (2) and length-measuring interferometer System (16) is connected.

6. white light interference lens center thickness measuring system according to claim 1, it is characterised in that also include, control The Mechatronic control system (18) of mobile support (151) motion.

7. white light interference lens center thickness measuring system according to claim 1, it is characterised in that also include, fixed Measured lens (11) and the adjustment frame (19) for adjusting measured lens (11) optical axis.

8. white light interference lens center thickness measuring system according to claim 1, it is characterised in that also including to measurement Temperature, the humidity of environment are gentle to press the environmental control system being controlled.

9. white light interference lens center thickness measuring system according to claim 1, it is characterised in that the very big white light The center of interference signal is judged by centroid algorithm.

10. the white light interference lens center thickness measuring system detection lens center thickness described in claim 1-9 any one Method, it is characterised in that comprise the following steps：

Step 1: data processing unit is calculated in temperature T according to the relevant parameter of input₁, pressure P₁With length-measuring interferometer system (16) laser head (162) wavelength X₁Under air refraction n₁, in temperature T₁, pressure P₁With super continuum source (1) wavelength X₂ Under air group index n₂, and in temperature T₂, pressure P₂With super continuum source wavelength X₂Group's refraction of lower measured lens (11) Rate n₃；

Step 2: regulation measured lens (11) and focusing lens (10) same to optical axis, makes the reflected light of measured lens (11) front and rear surfaces 1 can be returned to by focusing lens (10):1 fiber coupler (3)；

Step 3: the mobile support (151) of control does scanning motion, data processing unit along scanning corner reflector (13) optical axis direction The interference light signal that photodetector (2) is obtained is handled, the corresponding movement in very big interference light signal center is obtained The displacement Z of support (151)₁And Z₂；

Step 4: data processing unit is according to below equation：

<mrow> <mi>D</mi> <mo>=</mo> <mfrac> <mrow> <msub> <mi>n</mi> <mn>2</mn> </msub> <mo>&amp;CenterDot;</mo> <mn>2</mn> <mrow> <mo>(</mo> <msub> <mi>Z</mi> <mn>2</mn> </msub> <mo>-</mo> <msub> <mi>Z</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>n</mi> <mn>1</mn> </msub> <mo>&amp;CenterDot;</mo> <msub> <mi>n</mi> <mn>3</mn> </msub> </mrow> </mfrac> </mrow>

Calculating obtains the center thickness D of measured lens (11).